CVT vibration at 35-40 MPH under heavy acceleration

I know there are a lot of similar questions, and if you can spare a few minutes to read this I will appreciate it.

I have used the search function, and read a bunch of threads about belt slip/slap/squeak.
But I am not sure I have found quite the same issue as what I am experiencing.
I have done the thing where I hold the brake and go to 4000 rpm for a few seconds, and then smell the burn. I've done it a few times, to no avail.
I'm about 220lbs and I do hard acceleration quite often.

My 2008 Silverwing 600 has 10,500 miles. The belt is original. A thousand miles or so ago, right after I bought it used, I replaced the rollers with Dr Pulley sliders, and e verything was fine for a while.

What is happening now is that if I go for hard acceleration, it's all good up to about 35-40 MPH, where suddenly things change.
The engine does not rev, so I don't think it's a belt slip.
What does happen is that there is an odd throaty sound that sounds like the belt slapping the cover, and I can no longer feel it accelerating.
If I hold onto the throttle, after a couple of seconds it stops doing it.
If I ease the throttle at that point is stops doing that immediately, and then I can go for hard acceleration again.

It does not always happen if, for example, I'm already going 35 MPH when I go for hard acceleration.
It does not happen if my acceleration is gentle or intermediate.


I'm going into the garage now to pull the cover and inspect things.
I have a brand new belt on standby, and if I don't see anything obvious I'll try a new belt.

But I'm hoping for a fresh perspective on this.
I know you're probably all tired of answering belt/clutch questions, but if the way I have described this matches some fix that has been posted, please post a link because I didn't see it in my search. I saw a lot of possibly similar things, but none quite matched.

Thank you for your time.

Sounds to me like it could be that the rollers are sticking in the ramps. Check the rollers to be sure they are clean and not nicked or have flat spots. Also the ramps should be clean and free of any galled or rough areas. If this all is good, check the belt for any deformed areas. Since you are in the CVT consider replacing the rollers with Dr Pulley sliders. Their benefits are widely discussed and I love my 26gm sliders.

Thanks for the reply.

You must have missed the detail in my OP where I replaced the rollers with Dr Pulley sliders a thousand or so miles ago.

Since my OP, I have done some testing and looking around in there. I found that with the CVT cover off, the effect was GREATLY diminished. Still sort of happens - the pattern changes, the acceleration is slightly less, and the RPMs go down a bit - like when a clutch is doing its final engagement. But without the cover on, there is no belt slap to mess up the power band quite as much.

The cover shows quite a bit of belt wear on it.

I pulled the variator out and found that two of my sliders have wear on surfaces they shouldn't. But it is possible that happened when I initially installed them wrong and then fixed it, a thousand or so miles ago. Unfortunately when I pulled the variator out today the sliders fell out, so I did not get a chance to see if they had been in there right.

I just tried it again with the sliders definitely in right, and after cleaning out the ramps, and it seems the same. I'm about to put the cover back on and try one more time.

Then I'll try with the rollers back in, and then I'll try with the new belt in. I even have a spare set of sliders I could try.

I guess it's just a process of elimination I need to go through until it feels better.

It sounds like one or more of the sliders turned to one side when they were re-installed. But ScooterBJ was dead on with the rollers or sliders. If you still get the same shudder than maybe 1 or more of the sliders were damaged since you mentioned there is wear on a couple. Please tell us if you find the problem though since it will be a good learning experience for others. Good luck.

Just put the stock rollers back in. Still have the exact problem, complete with the belt slapping the CVT cover at just about 40 MPH, right when the RPM dips.

So I don't think the issue is roller/slider related. I suspect that slider wear on a facet of the slider that should not have seen wear probably happened when I first installed them (and installed them wrong), and then figured it out and got them in right.

I don't have the proper tool to measure my belt. I measured the width, and found it to be about .25 mm less than the new one. The book says from new to worn out is a 1 mm difference. But as I understand it the correct belt measurement requires a special tool that has a V shape and measurement marks, so I am not sure my width measurement is relevant.

But since I have a brand new belt sitting here, I'm trying that now.

OK, the verdict is in. It was the belt.

New belt + stock rollers = rough initial engagement, belt slap and RPM drop at 40 MPH gone.
New belt + Dr Pulleys back in = smooth power band all the way up, no belt slap and RPM drop.

I remember the rough initial engagement from before - that is why I put the sliders in there to begin with.
So, now I'm off to button up the outer covers and buy a new spare belt.

10,500 is too low a number for a belt life. But then, I have no idea how the scooter was treated for the first 9,000+ miles of its life. I can only start again with a new belt at 10,500 and see what happens next.

Install the new belt, but first clean the ramp and sliders, clean the inner and outer front drive faces with brake cleaner, do not lube anything on reassembly, and you should be good to go.

That has been done.

Scoundrel thank you for posting the question and follow up. Now if someone has the same problem they may find it with a search. Although it would probably would have been best to have put it in the Maintenance, Tips and Hints section.

You're welcome. I don't like it when I find a forum thread via search, and it matches my symptoms, and then a solution is never posted. It irritates me. So I try to always follow up when I can.

Regarding placement, I looked at the topic descriptions before posting, looking for something like "Troubleshooting" or "Technical Questions" or some such. The description for Maintenance, Tips and Hints made it sound more like a "HowTo" sort of place rather than a "What the heck is wrong with my machine?" sort of place.

Maintenance, Tips and Hints
"This section is for all of us to share information on performing maintenance for the Silver Wing. You can also post pictures here too to help others out too."

But if it's better categorized in that section, then any moderators may feel free to move it.

You may be right after all we all think different. I do hope you understand I didn't mean my post to sound like a put down or anything I was just typing without thinking. I usually search the category I think what I'm looking for should be but if I don't find it there then I search the whole site, so I'd probably find it wherever it was.

No worries, your wording did not come across negatively.
Looking in that section there are a lot of "help me" posts along with the "how to" ones, so I guess it would have fit in. But I can't move it now.

Brought this topic back to life because I'm having exactly the same problem as Scoundrel.

Bought the bike at about 15,000 miles, ran lovely. Had new stock belt and rollers at 16,000 miles by the dealer and noticed some vibration on pullaway but figured this was normal.

I've had the CVT and belt along with the rear clutch off the bike many times for cleaning etc. now showing 23,000 miles. The rear drum is scored from a previous numpty owner but the new pads seem to have 'bedded' in and it seems to be working OK.

The vibration described by Scoundrel is now a cause for concern. I've also noticed a 'clattering' noise coming from somewhere near the tunnel at motorway speeds and beyond. It sounds like a tappet but not quite so harsh. The engine sounds lovely when idling so I don't think it's a tappet. The 'clattering' seems to be 'in time' with the natural vibration expected from most bikes.

Is there a connection? My first think is the rollers or the slide plate, or both. I'm going to try Polini rollers first and then a new belt. I have a feeling I may have put the rollers in incorrectly during all the recent removals and done some damage.

It would be great if my symptoms and remedies turn out to be the same as Scoundrels.I know the miles don't point towards my suspicions but bikes are funny things.................aren't they?

Is there any blueing of the metal clutch drum. I ask because I've seen clutch drums that have been overheated and the blued patches of metal are consequently harder and, with continued wear, become the cause of clutch judder. In effect, the inside of the drum becomes "lumpy".

If it is severely blued, replace the drum. Re-machining the inside of the drum will not work satisfactorily.

The "Italian Tune-Up" remedy for belt slap/vibration of holding the brakes on and revving the engine to the maximum is therefore risky. I say only rev it for a MAXIMUM of 3 seconds and then let the engine idle for a couple of minutes to dissipate the heat. That worked on mine.

My first 2009 SilverWing had on again/off again clutch chatter thru out its 45,000 miles with me. Bike bought new, only ridden by me----no real fix.

My second 2013 has had belt chatter/vibration at steady 35-40mph=no fix, on third OEM belt. Just kinda nature of the beast

Interesting points guys. I have wondered about clutch judder. I'd replace the drum if it wasn't so expensive. The removal tool seems to be a bit evasive. I don't know where to get one so I'm thinking of having one made but it's complicated.

I'm waiting for my new rollers to arrive and I'll have another look at the clutch while I'm there. The other option is 'live with it', it's just what it does, but it didn't do any of this stuff when I first bought it. I'm curious. I'm planning to keep the bike forever as a project whatever happens. I reckon it could be a new(er) bike next year for us. What a dilema?

I gave it some welly on the way home from work today and it was bliss. Can't be too hard on the old girl, I reckon she's just nagging !

Having purchased and used 9 rubber band drive scooters for a total of over 400,000 miles. I feel this method is cheap for manufacture and fairly trouble free for most users----somehow I feel 125cc is about power limit for satisfactory and trouble free operation.

Three of the four Helix I had, had rear clutch bearing trouble...all covered by warrany, only broken belt was with Helix

Had 2 new Burgman 400's----one at 20,000 mi,whole rear clutch blew up, destroying everything in its way---under warranty, Suzuki paid, including new drive belt

I found in Korea my Daelim 125 scooter trouble free, and I noticed the pizza and noodle deliverymen had no problems with their drive belts, in spite of hard service. Dealer seldom replaced belts on the 125's

With SilverWing I carry spare belt. I change at Honda recommend intervals and with OEM belt AND make no mods to drive train (rollers/sliders,etc)---If I am unhappy with power/performance, I will simply get another bike...or might have one in garage. SilverWing works fine for me after at least 90,000 miles on two----Real problems are the weight and BUFFETING!!----If I have trouble in remote/strange place bike with all OEM parts easier to work and and have dealer get spares!

I was about to buy this one M40x1.0 thread tap but canceled order and I bought this one. Honda Puller.
If some day I must replace or repair greabox, I have this tool ready to use.

Took the drive train off just now.

Don't know what to make of these stock rollers.



The plastic inserts which guide the roller plate just fell out whereas the new ones I have are a good tight fit. Could this be causing some rattling?

I took the clutch assembly off and noticed grease on the clutch pads and inside the drum. (Clutch Judder?). The grease on the shaft seems to have turned to oil.



I used standard high temperature (or so it says) axle grease. I wonder if it's moving along the shaft and into the clutch drum?

Watching MotoGP right now so I'll get back to the bike later today.

The FWIW is coming from the factory is the shaft lubed and if it is what is used? It looks like the " oil " grease? is being contaminated, and turning dark. The only grease I've used on my cycles is the Honda Moly 60. If threaded bits need a touch I use Never Seize, very little goes a long way.

OK, so I cleaned up the clutch pads and the drum. I put Polini 26gm rollers in and roughed up the belt. Also took off some baked-on black belt remains from the pulley plates.

The bike feels 1000 per cent better. Still have the vibration under load at lower speeds but no belt slap and much better low end acceleration. The higher RPM seems to be as before with 5,500rpm at 70mph.

I did notice some 'blue tarnishing' on the clutch drum so I'm thinking that this is the main cause of the vibration, (see Flyingpanman's comments above). I have used Halford's all-purpose grease on the clutch shaft for now but I'm on the lookout for something a bit more specialized. I guess I'll have to change the drum and pads in due course but for now she's riding lovely, especially when riding light.

Could the vibration be caused by the tight fit of the sliding pieces? Is the vibration going up from 35 to 40 or down from 40 to 35? If it's coming down perhaps the sliders are holding the cones apart and the rollers are bouncing about a bit.
When I fitted my Dr Puley sliders I put in new sliding pieces too and they were very tight so I gently filed them with a small flat needle file to be a slight drag fit and they worked perfectly.

I see your point. I'm pretty sure they are not so tight as to prevent the roller plate from moving but I'll check it next time I'm in there. The vibration is only obvious while accelerating.

I can't feel any 'play' in any of the other rotating parts (apart from the famous 'clunk' from the final drive which is covered in a separate topic), so there's only the clutch left. The drum is very badly scored with blue tarnishing so it's obviously not working as it should.

If we put everybody's experiences and suggestions into the mix, I'm sure we'll get to the bottom of it to benefit all. Many say that it's just what the SW does but I'm not buying it.

Does this happen at a specific and consistent road speed or is it actually at a specific and consistent RPM?

Does it present continuously at that steady MPH or RPM?

If it turns out to be closely coupled to RPM, it is the variator and not the clutch.
If so, the rollers/slider could be moving unevenly (sticking) or they are unevenly worn.

If totally road speed related, it's the clutch.
Check the clutch shoes and springs, making sure the rubber dampener pieces are ALL installed and in good condition. Make sure the shoes pivot smoothly on the shaft. Uneven shoe wear from pivot shaft friction, or, weak clutch springs can alter dynamic balance causing vibration.
It is possible, but unlikely that the drum has become warped enough to effect the balance.

If the point that this vibration occurs is somewhat variable between road and engine speed, it is most likely belt vibration, if applying positive or negative torque, does the vibration cease?

Another point of interest is that I had a steady and repeatable vibration right around 4000rpm.

One of my tuning mods was to install a slightly stronger contra spring (somewhat a bone of contention here), this is the big spring that applies belt force to work against the roller weights.
The result of this is a slightly higher belt tension, so when in the midway position, where belt slap occurs, there is enough tension to prevent the vibration and slap.

At least it did with mine.

Interesting points. If I had to summarize it I would say that the vibration occurs at around 3000 - 4000rpm. This equates to around 25 - 40mph. (Roughly). I don't think it's vibrating on deceleration.

The clutch pads moved freely although they didn't settle fully into the rubber cushions without being pushed. This puzzled me because they can't be pushed back on their own when inside the drum !! Should the pads settle in on their own? if so, the rubber cushions must have swelled.

The blue tarnishing appears at six opposing spots around the drum. Is it warped?

The spring you mention had occured to me. Also, the belt is probably older than I think.

I'm going to ride it as it is and monitor the RPM/speed areas during the vibration more closely. I'll post my results.

As an aside, I love your profile picture. I've got my mate's Sporster in my garage, in pieces. It's been there for months now. He might have twice the cubic capacity but at least my wheels are turning. I just don't get the Harley thing

Yes, Honda reliability is KING!

I want to make a T-shirt that says